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SFM Quiz 2 (mine) > (L13) Principles of Genetic Inheritance > Flashcards

(L13) Principles of Genetic Inheritance Flashcards

1
Q

What does the term proband mean?

L9 S9

A

The person from whom a pedigree is initiated

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2
Q

What are characteristics of an autosomal recessive trait genotypically and on a pedigree?

L13 S10

A

Genotype:

-requires two copies of the gene for phenotype

Pedigree:

-present equal in both sexes -can skips generations

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3
Q

What are characteristics of an autosomal dominant trait genotypically and on a pedigree?

L13 S5-7

A

Genotype:

-Only requires 1 copy of the gene for phenotype

Pedigree:

  • present equal in both sexes
  • affected people have an affected parent (does not skip generations)
  • unaffected people do no transmit the trait (does not skip generations)
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4
Q

What are characteristics of an X-linked recessive trait genotypically and on a pedigree?

L13 S11

A

Genotype:

-one copy of gene on X chromosome for males; two copies for females for phenotype

Phedigree:

  • appears more frequently in males
  • males do not pass the trait on to sons but can pass it onto daughters
  • all daughters of affected males will at least be carriers
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5
Q

What are characteristics of an X-linked dominant trait genotypically and on a pedigree?

L13 S19

A

Genotype:

-requires only one gene in both males and females

Pedigree:

  • does not skip generations
  • all daughter of affected males are affected
  • half the sons of affected, heterozygous females are affected
  • carriers do not exist
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6
Q

What are characteristics of a Y-linked trait on genotypically and on a pedigree?

A

Genotype:

-males with allele are affected

Pedigree:

  • only appears in males
  • all sons of affected males are affected
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7
Q

How could you distinguish between an autosomal recessive trait with higher penetrance in males and an X-linked recessive trait?

A

A father could pass it to his son

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8
Q

Differentiate between monozygotic twins and dizygotic twins.

A

Monozygotic:

  • “identical” twins
  • share the same DNA sequence

Dizygotic:

  • “fraternal” twins
  • as similar DNA as normal siblings
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9
Q

Define concordiant trait and concordance.

A

Concordiant trait:

-trait shared by both members of a twin pair

Concordance:

-percentage of twin pairs that are concordant for a trait

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10
Q

What are characteristics of an mitochondrial inherited trait genotypically and on a pedigree?

L13 S12-14

A

Genotype:

-several mitochondria are present in each cell and a certain threshold of disease mitochondria are required for phenotype

Pedigree:

-only passed down my mothers

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11
Q

What is LHON?

What is its mechanism?

What are the symtpoms?

L13 S15

A

Leber’s hereditary optic neuropathy

Degeneration of retinal ganlion cells due to NADH dehydrogenase mutation resulting in not enough energy.

Results in loss of central vision

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12
Q

What is MERRF?

What is its mechanism?

What are the symtpoms?

L13 S16

A

Myoclonic epilepsy and ragged red fibers

Caused by a mutation in tRNA for lysine which disrupts cytochrome-c oxidase

Symptoms include ataxia and seizures

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13
Q

MELAS

What are the symtpoms?

L13 S17

A

Mitochondrial encehpalomyopathy, lactic acidosis, and stroke-like episodes

Symptoms typically neurologic or muscular

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14
Q

What do the terms euploid, polyploid, and aneuploid mean?

L13 S21

A

Euploid:

-normal number of chromosomes

Polyploid:

-complete extra set of chromosomes

Aneuploid:

-missing or additional individual chromosomes

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15
Q

What is the result of nondisjunction?

L13 S22

A

Trisomy and monosomy

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16
Q

What is genomic imprinting?

L13 S23;25-26

A

Pattern of DNA methylation and histone modificaiton that results in selective gene silencing without alteration of DNA sequence.

Imprinting occurs gametogenesis and is unique to the sex of the parent. During division of somatic cells, imprinting patterns are maintained.

17
Q

What is uniparental disomy and how does it occur?

When can it cause issues?

L13 S23-24

A

Condition in which an individual has two copies of a chromosome from a single parent and no copy from the other parent.

Occurs due to errors in mitosis or early fetal development.

Typically this is not a problem unless a gene that is affected is imprinted and therefore there is no functional copy of that gene.

18
Q

What are the main types of chromosomal mutations?

L13 S27

A

Inversion:

-segment of DNA is in reverse order of normal

Deletion

Duplicaiton

Translocation:

-exchange of DNA on two seperate chormosomes

19
Q

What is the karyotype of Turner syndrome and what is the sex of the individual?

What are the key symptoms?

L13 S30

A

Females with a karyotype of 45, XO

Major symptoms:

  • short stature
  • webbed neck
  • no puperty; no secondary sex traits, ammenorrhea
20
Q

What are Prader-Willi and Angelman syndromes and what are the symptoms?

What is special about them?

L13 S31

A

Both result from deletion a portion of chromosome 15. The region contains two imprinted genes, one paternal and one maternal. Which parents chromosome the deletion occured on results in one of the two syndromes.

Prader-Willi syndrome:

  • deletion of region on paternal chromosome
  • uncontrolled eating, intellectual disability, short stature

Angelman syndrome:

  • deletion of region on maternal chromosome
  • severe intellecutal diability, seizures, ataxia
21
Q

What is the karyotype of Klinefelter syndrome and what is the sex of the individual?

What are the key symptoms?

L13 S32

A

Males with karyotype of 47, XXY

Major symptoms:

  • hypogonadism and small testes
  • parital female secondary sex characteristics
  • tall stature
  • cognitive, behavioral, and learning difficulties
22
Q

What is trisomy 21 and what are the main characteristics?

L13 S33-34

A

Downs syndrome

Characteristics:

  • cognitive impairment
  • flattened nose and face, upward slanting eyes
  • caridac defects
  • duodenal atresia
23
Q

What is trisomy 18 and what are the characteristics?

L13 S35

A

Edwards syndrome

95% die in utero, few survive to 1 year

Characteristics:

  • microencephaly with prominent occiput
  • malformed ears
  • overlapped fingers
  • rocker bottom feet
24
Q

What is trisomy 13 and what are the characteristics?

L13 S36

A

Patau syndrome

Most die in utero, few survive past 1 week

Characteristics:

  • cleft lip/palate
  • close spaced or absent eyes
  • clenched, polydactyl hands
  • microcephaly
25
Q

What is variable expressivity?

L13 S39

A

Range of phenotypes possible from individuals with the same genotypes

26
Q

What is Marfan syndrome?

L13 S40

A

Defect in fibrilin resulting in variable effects in connective tissue.

27
Q

What is locus heterogeneity?

L13 S41

A

Single disorder, trait, or pattern of trait caused by a mutation of at least one of a group of genes.

eg. Osteogenesis imperfecta

28
Q

What is penetrance?

L13 S38

A

The rate at which a phenotype is actually present in people with the associated genotype.

29
Q

When are probabilities added or multiplied?

L13 S44

A

Added:

-when considering the probability of “one or the other” occuring

Multiplication:

-when considering the probability of multiple outcomes occurring together

30
Q

What is the difference between allele frequency and genotype frequency?

L13 S46

A

Allele frequency:

  • frequency of alleles present in a population
  • ie. A:a
  • remember all individuals have 2 alleles
  • does not indicate frequency of genotypes

Genotype frequency:

-frequency of genotypes in a population -ie. AA:Aa:aa

31
Q

What is the Hardy-Weinberg principle and what is it used for?

L13 S48

A

p^2+2pq+q^2

Specifies the relationship between gene/allele frequency (p:q) to genotype frequency

32
Q

What does the term consanguineous mean and what are the implications?

L13 S52

A

Mating occuring between closely retaliated individuals.

Mortality rates of offspring are increase (9% increase between first cousins)

33
Q

What is heteroplasmy?

L13 S18

Panini pg. 330

A

Becuase there are multiple mitochondira per cell, there are also multiple copies of mitochondiral DNA.

Diseases involving mitochondrial DNA do not follow typical dominant and recessive phenotypes and instead diseased mitochondira must exceed a certain therhsold of prevalence for symptoms to occur.

Threshold often gets lower with age so somebody who may not have had symptoms at a younger age could develop them later in life.

SFM Quiz 2 (mine) (25 decks)

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